Up until a number of years ago a large number of sports were practiced on natural turf. Natural turf has the advantage that it is relatively soft and wounds and injuries are thereby seldom caused during falls, sliding tackles and the like. The great drawback of natural turf however is that it can deteriorate significantly in quality due to intensive use and/or weather conditions. What remains is a badly damaged field with large, bare (sand) surfaces which cannot be played on, or only with difficulty, and which have an unattractive appearance.
Synthetic grass surfaces have therefore already existed for a number of years, in particular for hockey, tennis and the like. Synthetic grass surfaces require less maintenance and withstand a more intensive use than natural turfs. However, the drawback of synthetic turf is that the frictional resistance is so high that wounds and/or injuries can be caused in the case of sliding tackles and undesired falls.
In the present application the terms "grass surface" and "turf" are used interchangeably.
Therefore a hybrid turf or combination turf has already been proposed in the above mentioned patent document WO-A-9400639, in which the advantages of both types of turf are combined. This combination turf is formed by a conventional synthetic grass surface constituting a base layer on which a layer of growth substrate is strewn. Grass seed is sown into this growth substrate, so that the crowns of the grass lay between the synthetic grass fibers and are protected thereby. The synthetic grass is formed by a backing and a great number of upright synthetic grass fibers connected therewith. The synthetic grass fibers are regularly spaced, and may be connected to the backing by tufting or weaving. The backing is perforated, so as to allow water and roots of the natural grass to pass therethrough. As backing a coarse woven material is for instance proposed, wherein apertures are formed between the warp and weft threads. It is further proposed to construct the backing from two layers, an apertured top layer carrying the synthetic fibers and a bottom layer stabilizing the top layer with the fibers and preventing the fibers from becoming unstuck during handling of the synthetic grass. The bottom layer may be made from a biodegradable material, so that this will gradually disappear after the turf has been laid, leaving only the perforated top layer with the synthetic grass fibers.
In this known combination turf the emphasis is mainly on the synthetic grass, and there is relatively little room for growing a robust natural grass turf. Furthermore, the cost of the known combination turf is relatively high.